I've managed to fix the battery, and considering how much I've struggled to find information on it (and how to do it), here's what I did (along with some photos) so somebody else doesn't need to struggle as much.
WARNING: This procedure is very dangerous and if you're not EXTREMELY careful, you will start a fire or an explosion, and possibly hurt yourself badly. Do this at your own risk, outside, with eye protection and only if you're experienced with electronics.
TL;DR: The main connection between the cells and the BMS was loose - it needed to be tightened. It seems that a certain batch of these batteries has this specific problem as I've seen people explain the issue but nobody had a fix for it.
This model doesn't lock itself out if you disconnect the cells from the BMS (although I didn't disconnect the flat cable used for cell balancing and monitoring, so keep that in mind).
Orientation: Bottom part = the part where the connector and the power button of the battery is. Top part = the part to which the battery clicks into the bike and to which the lock engages.
Note: Make sure to take photos during the whole process so you know what goes where and how.
Steps:
1. On the top, unscrew the plastic part of the battery with the notch mechanism that the battery lock latches on (2x small phillips). This will leave you with another plastic cover that actually holds the cells beneath.
2. Unscrew the 4 torx screws that hold the top part. One of the screws will have a blob of resin used to block you out from unscrewing it. Use a hot air soldering station to soften it, then use hard tweezers or an extra small screwdriver to get it out and allow access to the screw. Pull out the plastic plate along with the rubber seal. Insert the rubber seal into the plastic plate you just removed. Now you're done with the top part.
3. On the bottom part, unscrew the 4 torx screws that hold the plastic plate that contains the connector, the LEDs and the power button (glued on the side). The situation with the blob is the same - you'll need to remove the blob to access 1 of 4 screws. Once you do, you'll have to ungue the power button. Do not use IPA to dissolve the glue as it will just separate the power button into two parts. Rather, carefully scrape underneath the power button while making sure you don't damage the weak flexible PCB that extends underneath. The point is that you have to completely move the power button away from the aluminimum housing the of the battery so it only hangs out of the bottom plastic plate.
DO NOT pull on the plastic plate. Just unscrew it and unstick the power button.
4. Now, you'll have to push out the battery, the BMS and the bottom plate out of the metal housing. This is the hardest part, as all the cells are encased in a plastic/rubber combo all along its length. On the floor, place a flat object that can fit inside the top part of the battery (from step 2) and then flip the battery and place the inner part of it on that object so you can use all your strength to grab the aluminimum housing and push it down towards the floor. This will slowly start pushing out the BMS/Connector/LED/Power Button plate along with the cells. It will take some time, and
do not succumb to using a rubber hammer or something like that, as the rubber along the cells won't budge - It needs consistent hard pressure, not instantenous short burts. Also, NEVER pull the plastic place that holds the connector/bms.
5. Once the cells are out, you'll have full access to the BMS. It consists of 3 plates:
First plate is the one that has the charging connector and the LEDs and the button.
Second plate is a separator plate that also guards the BMS circuitry.
Third plate actually holds the BMS circuitry and is attached to the cells using a sliding mechanism (slides from top to center). Do not separate the first plate from the 2nd plate.
6. Carefully separate the second plate from the third plate by undoing the two notches on the sides. This will allow you access to the BMS board, but be careful not to separate it by more than 1cm.
7. You'll now see that, at the top, there's 2 flat cables. One of them is attached to the flexible PCB that goes to all the cells and monitors/balances them. The second flat cable goes to the first plate and connects to LEDs and the power button. Remove the second flat cable by lifting the flat cable lock (black part of the connector) and pulling it out.
8. You'll also see there's a white connector with 2 wires out of it. These are the CANbus wires. Unplug the connector.
9. You're now left with 3 thick wires which are the output from the BMS towards the main power connector (negative, positive (36V), and probably ground?), and a flat cable for cell monitoring/balancing (do not disconnect it).
10.
You can now slightly angle the first and second plate together from the third plate. This will allow you to see two thick flat copper plates with a V shaped hole in them so they can slide onto the bolts on the BMS. They are the main culprit. Those are the wires that go from the cells into the bms. They're connected to the BMS with 2 nuts and they were loose in my case. Find the right tool for those two nuts (don't ask me what I used), but MAKE SURE not to touch anything else on the board or else you're fry it or cause a fire. Untighten those two nuts by 1 turn, then make sure to slide the third plate nicely so the bolts and nuts fit into the copper plates. Then, tighten the nuts REALLY hard as you don't want them going loose again due to the vibrations. This will secure the connection between the cells and the BMS and you're done.
11. Reconnect the LEDs/Button flat cable. Test that the battery still works by pressing the (now hanging in mid air) power button.
12. Reconnect the CANbus (white) connector to the BMS board.
13. Now piece together all the plastic plates while making sure the flat cables are folded between the third and the second plate. Be very mindful as in the next step, you'll push on all these plastic plates in order to get the entire battery back into the aluminimum housing.
14. You can now push back in the inner part of the battery (cells, BMS, plates, etc) into the aluminium housing. Use slow but consistent force do it. When you get close to the end, watch closely to make sure the BMS and connector plates fit cleanly into the alumimum housing and that no wires/flat cables are hanging on the side (because they'll get damaged by the casing).
15. Once pushed all the way in, screw the 4 torx screws in a diagonal pattern (1-4-3-2) by a bit multiple times to make sure it evenly closes. This will push the battery in completely and you'll be done.
16. Now screw other plastic plate of the battery (on the other side of the aluminum casing), while making sure the rubber gasket fits nicely.
17. Screw in the notch/locking plate with 2x phillips screws.
18. You're done. Test out the battery and it won't throw any temperature errors anymore.
